The fabrication processes generally employed to obtain a finished ophthalmic lens trimmed to the shape of a particular frame typically include steps during which the ophthalmic lens receives markings on its surface. For example, the lens may receive dots or crosses identifying a particular point (for example the optical center of the ophthalmic lens), axis lines (for example to indicate the axis on which astigmatism is corrected), shapes delimiting a particular area (for example near vision area or distant vision area in the case of progressive ophthalmic lenses). Likewise, it may be necessary to effect markings relating to the identification of the ophthalmic lens or other commercial markings.
Of the diverse technologies for causing a mark to appear on the surface of an ophthalmic lens, marking with the aid of an inked pad applied to said surface is routinely employed for its low operating cost and its marking accuracy.
Thus there are known processes for depositing ink onto an ophthalmic lens during which an ophthalmic lens is disposed on a support in the vicinity of a plate with engravings reproducing the shapes to be printed on the lens, this plate being commonly referred to as a “printing plate”.
The printing plate and the ophthalmic lens are both accessible to an elastically deformable pad, generally of silicone. The pad is first applied to the surface of the printing plate after it has been inked (i.e. after the engravings on the printing plate have been filled with ink). The pad is then moved away from the surface of the printing plate, the ink contained in the engravings adhering to the pad to form an inked pad.
The inked pad is then applied to the surface of the ophthalmic lens to be marked and the ink disposed in the engravings on the printing plate is then transferred from the pad to the surface of the ophthalmic lens.
A method of printing markings on a progressive ophthalmic lens is also known from the document US 2003/0107704. This method deposits on an ophthalmic lens a pattern that includes a graduated portion.
This method can therefore be used to print the same pattern on progressive ophthalmic lenses with different characteristics. The graduations are used afterwards to identify particular points specific to each type of lens.
Thanks to this method, it is therefore not necessary to have a marking specific to each of the types of progressive ophthalmic lenses.